With electrical appliances becoming ubiquitous in recent years, safety of appliances is of paramount concern to manufacturers and users of the appliances. A widespread use of electrical appliances can be seen in day-to-day life in residential as well as business establishments. Electrical appliances generally operate on A.C mains supply delivered through electrical installations in residential as well as commercial establishments. Typically, electricity directing devices are mounted as electrical installations in industrial and residential environments comprising slots or holes that receive electricity through distribution lines and direct the electricity to one or more appliances that operate using electricity. Examples of electricity directing devices include, but are not limited to, wall sockets, power outlets, power points, extension cables, or power strips etc.
Safety and health regulations in most of the countries necessitate the use of safety fuses for protecting electrical appliances connected to electricity directing devices. A safety fuse is an electrical device that interrupts flow of current through an electrical appliance or an electric current by detecting passage of overload current through the appliance and disconnecting power supply from the rest of the circuit. Overload current is defined as current value greater than which an appliance or an electric circuit is designed to pass through safely. Classically, an overload current to burn a safety fuse is 2 to 5 times the magnitude of a circuit's normal operating current value. If the overload current in an electric circuit is not detected and the circuit is not disconnected, it may damage other elements of the device or may melt power supply wires.
Characteristically, a safety fuse consists of a metal wire or an alloy wire element arranged in series with the appliance or electric circuit and is designed to carry current passing through the appliance. The safety fuse is a sacrificial element specifically constructed with a rated current value so that if normal current flows through it, the appliance works normally. However, if a current value more than melting integral value (I2t) is passed through the fuse for a specific time, the fuse element melts down. Melting integral value of a fuse indicates a thermal value required to melt a specific fuse element. For a particular fuse element, construction, materials and cross sectional area of the fuse element determines the melting integral value of the fuse. The fuse element is usually made up of a material such as zinc, copper, silver, aluminum or other alloys. Melting of the fuse element breaks down the circuit and avoids damage to elements of the circuit.
Since contemporary safety fuses allow passing of overload current through the load for a specific time before melting out, in some cases, the time may be sufficient for the electrical load to be damaged or an electrical hazard to occur. Moreover, since the fuse is a sacrificial element, a user has to replace the fuse once it melts in order to be able to use the load again. Also, since each load has a different overload current value, a distinct safety fuse is required to be used for a distinct load.
In light of the limitations associated with using a safety fuse, there is a need to have an advanced method and system for protecting electric appliances and circuits so that any damage to the appliances due to overload current is avoided.